TW201908421A - Conductive coating liquid composition and transparent conductive film for flexible display comprising the conductive layer thus produced - Google Patents

Abstract

The invention relates to a conductive coating liquid composition and a transparent conductive film for a flexible display containing a conductive layer manufactured by the conductive coating liquid composition. Even if the transparent conductive film is bent for multiple times, surface resistance variation is still little, the haze is low, the light transmittance is high, and thus the transparent conductive film is suitable for a flexible display.

Description

Conductive coating liquid composition and transparent conductive film for flexible display including conductive layer manufactured thereby

The present invention relates to a conductive coating liquid composition and a transparent conductive film for a flexible display including a conductive layer manufactured therefrom. Even after the transparent conductive film is bent multiple times, the surface resistance changes are still small, the haze is low, and the light is transmitted. The high rate makes it suitable for flexible displays.

At present, the material of the most widely used transparent electrodes for displays is indium tin oxide (ITO). However, the formation of a transparent electrode using ITO has the following disadvantages. Not only is an excessive cost, but it is difficult to realize a large area. In particular, when ITO is applied over a large area, there is a disadvantage that the brightness and luminous efficiency of the display are reduced because the surface resistance changes greatly. In addition, indium, which is the main raw material of ITO, is a rare mineral, which is rapidly drying up as the display market expands. In order to overcome these shortcomings of ITO, poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate, PEDOT / PSS, which has excellent flexibility and simple coating process, is being used. ) Research on forming transparent electrodes.

On the other hand, recently, as the use of liquid crystal display elements is increasing, the use of constituent materials is also increasing. Among them, various transparent plastic materials that replace materials such as metal or glass are widely used in parts requiring high transparency. Among them, since the surface of the panel of the liquid crystal display element is exposed to the outside, a transparent substrate for protecting the panel from various external stimuli is widely used.

However, when a display is formed using PEDOT / PSS as a transparent electrode and polyethylene terephthalate (PET) as a transparent substrate, unreacted oligomers emerge from the PET during the heat treatment process. To the surface, thereby increasing the haze value or damaging the transparent electrode, resulting in an increase in surface resistance. In addition, since the change in surface resistance after a large number of bendings is large, it is not suitable for a flexible display that requires high physical stability after a plurality of bendings (see Korean Laid-Open Patent No. 2011-0095915).

Therefore, an object of the present invention is to provide a conductive coating liquid composition and a transparent conductive film including the conductive layer manufactured therefrom. Even after repeated bending, the surface resistance changes are still small, the haze is low, and the light transmittance is high. As a result, a conductive layer suitable for a flexible display can be manufactured.

In order to achieve the above object, the present invention provides a conductive coating liquid composition comprising poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT / PSS). , Organic binders, organic solvents, silane coupling agents and surfactants.

To achieve another object, the present invention provides a transparent conductive film for a flexible display, including a transparent base film and a conductive layer, wherein the conductive layer is formed of the conductive coating liquid composition.

The transparent conductive film for a flexible display of the present invention includes a conductive layer formed of a conductive coating liquid composition. The transparent conductive film has the following advantages. Even after repeated bending, the surface resistance changes are still small, the haze is low, and the light is transmitted. The rate is high.

The conductive coating liquid composition of the present invention includes poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT / PSS), an organic binder, and an organic solvent. , Silane coupling agent and surfactant.

The conductive coating liquid composition may include 10 to 70 wt% PEDOT / PSS, 1 to 20 wt% organic binder, 10 to 80 wt% organic solvent, 0.05 to 1 wt% silane coupling agent, and 0.02 to 0.4 wt % Surfactant. Specifically, the conductive coating liquid composition may include 30 to 60 wt% of PEDOT / PSS, 1 to 10 wt% of an organic binder, 40 to 65 wt% of an organic solvent, 0.1 to 1 wt% of a silane coupling agent, and 0.1 ~ 0.4wt% surfactant. More specifically, the conductive coating liquid composition may include 35 to 50 wt% of PEDOT / PSS, 1 to 5 wt% of an organic binder, 45 to 60 wt% of an organic solvent, 0.5 to 1 wt% of a silane coupling agent, and 0.1 ~ 0.4wt% surfactant.

The PEDOT / PSS is a water-dispersible conductive polymer doped with poly (4-styrenesulfonate) (PSS) in poly (3,4-ethylenedioxythiophene) (PEDOT). The PEDOT / PSS has a ring-shaped ethylene dioxy group in a thiophene structure, and has an electron supply effect through ethylene dioxy groups substituted at the 3 and 4 positions, which has a lower effect than that of thiophene. The optical band gap (760nm ~ 780nm or 1.6eV ~ 1.7eV) can change color according to the oxidation / reduction potential difference. Under the oxidation state, there is an absorption band in the infrared region to ensure transparency.

The organic binder may include one or more selected from the group consisting of a melamine resin, a polyester resin, a urethane resin, and a polyacrylic resin. In addition, the organic binder may be a water-dispersible resin.

The weight average molecular weight of the organic binder may be 5000 to 30,000 g / mol. Specifically, the weight average molecular weight of the organic binder may be 10,000 to 20,000 g / mol.

The organic solvent may include an alcohol-based organic solvent and an amidine-based organic solvent. Specifically, the organic solvent may include an alcohol-based organic solvent and an amidine-based organic solvent in a weight ratio of 10 to 30: 1. More specifically, the organic solvent may include an alcohol-based organic solvent and an amine-based organic solvent in a weight ratio of 10 to 25: 1, a weight ratio of 15 to 25: 1, and a weight ratio of 17 to 25: 1. When the mixing ratio of the alcohol-based organic solvent and the amidine-based organic solvent is within the above range, the conductivity is increased after the conductive coating liquid composition is applied, so that a coating layer having a low surface resistance can be obtained.

The alcohol-based organic solvent plays a role of improving the coatability by reducing the surface tension of the conductive coating liquid composition. Specifically, the alcohol-based organic solvent may be an alcohol having 1 to 4 carbon atoms. More specifically, it may be methanol, ethanol, propanol, isopropanol, or n-butanol.

The ammonium organic solvent plays a role of improving the conductivity of the prepared conductive layer. Specifically, the amidamine-based organic solvent may include one or more selected from the group consisting of acetamide, N-methylacetamide, N-dimethylacetamide, and N-methylpyrrolidone.

The silane coupling agent plays a role of facilitating the lamination of a conductive layer on a transparent base film by improving the adhesion of the conductive coating liquid composition. Specifically, the silane coupling agent may include one or more selected from the group consisting of trimethoxysilane, triethoxysilane, tetramethoxysilane, and tetraethoxysilane.

The triethoxysilane may be 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane (2- (3,4-epoxycyclohexyl) ethyltriethoxysilane), (3-aminopropyl ) (3-aminopropyl) triethoxysilane, (pentafluorophenyl) triethoxysilane, (3-glycidyl etheroxypropyl) triethoxysilane ( (3-glycidyloxypropyl) triethoxysilane) or (4-chlorophenyl) triethoxysilane.

The trimethoxysilane may be (3-glycidyloxypropyl) trimethoxysilane, (3-chloropropyl) trimethoxysilane ((3-chloropropyl)) trimethoxysilane), (3-mercaptopropyl) trimethoxysilane, (3-mercaptopropyl) trimethoxysilane, (3-aminopropyl) trimethoxysilane, [3- (2-amino Ethylamino) propyl] trimethoxysilane ([3- (2-aminoethylamino) propyl] trimethoxysilane), (N, N-dimethylaminopropyl) trimethoxysilane ((N, N-dimethylaminopropyl) trimethoxysilane) ), (3-bromopropyl) trimethoxysilane or (3-bromopropyl) trimethoxysilane.

The surfactant may be a silicon-based surfactant or an acetylene-based surfactant.

The silicon-based surfactant may be a modified silicon-based surfactant. For example, BYK-378 of BYK is a commercially available product of the silicon-based surfactant.

For example, the commercially available product of the acetylene-based surfactant is Dynol 604 of Air Products.

The conductive coating liquid composition may further include a pH adjuster. Specifically, the pH adjusting agent may include a member selected from the group consisting of 2-dimethylaminoethanol, 2,2'-iminodiethanol, and 2,2 ', 2' ' -One or more of the group consisting of nitrilotriethanol (2,2 ', 2' '-nitrilotriethanol).

Based on the total weight of the conductive coating liquid composition, a pH adjuster may be included in an amount of 0.001 to 0.01% by weight. Specifically, based on the total weight of the conductive coating liquid composition, a pH adjuster may be included in an amount of 0.001 to 0.005 wt%.

The transparent conductive film for a flexible display of the present invention includes a transparent base film and a conductive layer formed of a conductive coating liquid composition including PEDOT / PSS, an organic binder, an organic solvent, a silane coupling agent, and a surfactant. .

The conductive layer is formed of a conductive coating liquid composition including PEDOT / PSS, an organic binder, an organic solvent, a silane coupling agent, and a surfactant. The conductive coating liquid composition is as described above.

The average thickness of the conductive layer may be 100-1000 nm. Specifically, the average thickness of the conductive layer may be 100-700 nm.

The transparent base film may include polyethylene terephthalate (PET), polyimide (PI), or colorless transparent polyimide (PI). Specifically, the transparent base film may be composed of polyethylene terephthalate (PET) or colorless transparent polyimide (PI).

The average thickness of the transparent base film may be 12 to 200 μm. Specifically, the average thickness of the transparent base film may be 15 to 150 μm, 15 to 130 μm, or 20 to 130 μm.

The transparent conductive film can be bent 300,000 times under a state of applying a voltage of 5V so that the bending radius reaches 3 mm, and then the surface resistance change calculated using the following formula (1) may be -5.0 to 5.0%. Specifically, the transparent conductive film may be bent 300,000 times under a state of applying a voltage of 5V, so that the bending radius reaches 3 mm, and then the surface resistance change calculated using the following formula (1) may be 0 to 5.0%.

[Formula 1]

The surface resistance of the transparent conductive film is 100 to 200 Ω / □ or 150 to 200 Ω / □, and the haze measured after cutting into 10 cm × 10 cm × 50 μm (length × width × thickness) is less than 1%. Specifically, the surface resistance of the transparent conductive film is 100 to 180 Ω / □, and the haze measured after being cut into 10 cm × 10 cm × 50 μm (length × width × thickness) is less than 0.7%.

The transparent conductive film may have a transmittance of visible light of more than 80%, and a contact angle with water may be 60 to 85 °. The transparent conductive film may have a transmittance of visible light of more than 80%, and a contact angle with water may be 63-84 °.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

[Example]

The manufacturers and product names of the compounds used in the following examples and comparative examples are shown in Table 1 below.

Table 1

Example 1. Preparation of transparent conductive film

42.9g of water-dispersed PEDOT-PSS, 2.524g of organic binder-1, 0.9g of silane coupling agent-1, 0.3g of surfactant-1, 0.003g of pH adjuster, 2.6g of organic solvent -1 and 50.773 g of the organic solvent-2 were mixed to obtain a conductive coating liquid composition. Then, the conductive coating liquid composition was wet-coated on one side of a PET-based film (manufacturer: SKC, trade name: TU63, average thickness: 50 μm), dried at 80 ° C. for 3 minutes, and thermally cured. A conductive layer having an average thickness of 620 nm was formed, thereby preparing a transparent conductive film having an average thickness of 50.62 μm.

Examples 2 to 8.

Except changing the types and contents of PEDOT-PSS, organic binder, silane coupling agent, surfactant, pH adjuster and organic solvent, a transparent conductive film with an average thickness of 50.62 μm was prepared by the same method as in Example 1. .

Table 2

Example 9.

A transparent conductive film having an average thickness of 50.62 μm was prepared in the same manner as in Example 1 except that the base film used a polyimide film (manufacturer: SKC, trade name: CtPI, average thickness: 50 μm).

Experimental example 1. Evaluation of physical properties of transparent conductive film

The physical properties of the transparent conductive films of Examples 1 to 9 were evaluated as described below, and are shown in Table 3.

( 1 ) Surface resistance

The transparent conductive film was cut into 500 mm × 500 mm (length × width), and the surface resistance of the conductive layer was measured using MCP-T370 from Mitsubishi Chemical Analytech.

( 2 ) Haze

The transparent conductive film was cut into 10 cm × 10 cm × 50 μm (length × width × thickness), and the haze was measured using NDH2000N of Nippon Denshoku Company in accordance with the ISO 14782 standard.

( 3 ) Transmission

The NDH2000N from Nippon Denshoku was used to measure the transmittance of the transparent conductive film to visible light (380 ~ 780nm).

( 4 )Contact angle

The transparent conductive film was cut into 1 cm × 5 cm × 50 μm (length × width × thickness), and a drop of water was dropped. The angle between the surface of the coating film and the tangent of the water droplet was measured to determine the contact angle.

( 5 ) Adhesiveness (cross cutting, cross hatch cut )

The transparent conductive film was cut into 20 m × 20 cm × 50 μm (length × width × thickness), and the adhesion by cross cutting was measured in accordance with the ISO 2409 standard.

table 3

Experimental example 2. Evaluation of the flexibility of a transparent conductive film

In order to evaluate the flexibility of the transparent conductive films of Examples 1 and 9, the transparent conductive film was cut into 15 mm × 50 mm (length × width), and then the cut transparent conductive film (hereinafter, referred to as a sample) was mounted opposite to each other. On the fixture. Adjust the length of the sample between the two clamps from 50mm to 13mm, so that the clamps on both sides are adjacent to each other, and the sample in between becomes a bending structure with a bending radius of 1mm or 3mm and a bending of 300,000. During this period, a voltage of 5 V DC was applied and the surface resistance was measured. In addition, the bending makes the conductive layer outward (stretching) or inward (compressing) when folded, and measures the maximum and minimum values of the surface resistance and the surface resistance after 300,000 times of bending. Table 4 shows the measurement results of the film of Example 1, and Table 5 shows the measurement results of the film of Example 9.

Table 4

table 5

As shown in Tables 4 and 5, the rate of change in surface resistance after bending of the transparent conductive film of the example was small, and the surface resistance after bending was within a measurement error range before bending.

Experimental example 3. Evaluation of metal adhesion of a transparent conductive film

According to the vacuum degree, linear speed, pretreatment conditions and film forming conditions in Table 6, a metal layer, such as copper (Cu) or silver ( Ag). Thereafter, the physical properties were evaluated as described below and shown in Table 7.

Table 6

( 1 Resistivity ) And surface resistance

The transparent conductive film was cut into 10 cm × 10 cm (length × width), and the resistivity and the surface resistance of the conductive layer were measured using MCP-T370 from Mitsubishi Chemical Analytech.

( 2 ) Adhesiveness (cross cutting, cross hatch cut )

The transparent conductive film was cut into 20 m × 20 cm × 50 μm (length × width × thickness), and the adhesion by cross cutting was measured in accordance with the ISO 2409 standard.

Table 7

As shown in Table 7, it can be seen that the transparent conductive film of the present invention has not only excellent metal adhesion, low surface resistance after metal deposition, but also good appearance, so it is suitable for narrow bezel displays.

100‧‧‧ transparent conductive film

10‧‧‧ conductive layer

20‧‧‧ transparent base film

30‧‧‧ metal layer

FIG. 1 is a cross-sectional view of a transparent conductive film for a flexible display according to an embodiment of the present invention.

2 is a cross-sectional view of a thin film with a metal layer laminated on one surface of a transparent conductive film for a flexible display according to an embodiment of the present invention.

Claims (19)

A conductive coating liquid composition comprising a poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT / PSS) and an organic binder , An organic solvent, a silane coupling agent, and a surfactant. The conductive coating liquid composition according to item 1 of the scope of the patent application, wherein the conductive coating liquid composition includes 10 to 70 wt% of PEDOT / PSS, 1 to 20 wt% of the organic binder, and 10 to 80% by weight of the organic solvent, 0.05-1% by weight of the silane coupling agent, and 0.02-0.4% by weight of the surfactant. The conductive coating liquid composition according to item 1 or 2 of the patent application scope, wherein the organic binder contains one or more members selected from the group consisting of a melamine resin, a polyester resin, a urethane resin, and a polyacrylic resin. The conductive coating liquid composition according to item 1 or 2 of the scope of application for a patent, wherein the organic solvent comprises an alcohol-based organic solvent and a monoamine-based organic solvent. The conductive coating liquid composition according to item 4 of the scope of patent application, wherein the alcohol-based organic solvent is an alcohol having 1 to 4 carbon atoms. The conductive coating liquid composition according to item 4 of the scope of application for a patent, wherein the ammonium organic solvent comprises a solvent selected from the group consisting of acetamide, N-methylacetamide, N-dimethylacetamide, and One or more of the group consisting of N-methylpyrrolidone. The conductive coating liquid composition according to item 4 of the scope of patent application, wherein the organic solvent includes the alcohol-based organic solvent and the amidine-based organic solvent in a weight ratio of 10 to 30: 1. The conductive coating liquid composition according to item 1 or 2 of the scope of the patent application, wherein the silane coupling agent comprises a material selected from the group consisting of trimethoxysilane, triethoxysilane, tetramethoxysilane, and One or more of the group consisting of a tetraethoxysilane. The conductive coating liquid composition according to item 1 or 2 of the scope of the patent application, wherein the surfactant is a silicon-based surfactant or an acetylene-based surfactant. The conductive coating liquid composition according to item 1 or 2 of the patent application scope, wherein the conductive coating liquid composition further comprises a pH adjuster. The conductive coating liquid composition according to item 10 of the scope of application for a patent, wherein the pH adjusting agent is selected from the group consisting of 2-dimethylaminoethanol, 2,2'-iminodiethanol (2 , 2'-iminodiethanol) and 2,2 ', 2' '-nitrilotriethanol (2,2', 2 ''-nitrilotriethanol). The conductive coating liquid composition according to item 10 of the scope of application for a patent, wherein the conductive coating liquid composition contains 0.001 to 0.01 wt% of a pH adjuster based on the total weight of the conductive coating liquid composition. A transparent conductive film for a flexible display includes a transparent base film and a conductive layer. The conductive layer comprises a poly (3,4-ethylenedioxythiophene / polystyrene sulfonate (poly (3,4- A conductive coating liquid composition of ethylenedioxythiophene) / polystyrene sulfonate; PEDOT / PSS), an organic binder, an organic solvent, a silane coupling agent, and a surfactant is formed. The transparent conductive film for a flexible display according to item 13 of the scope of the patent application, wherein the conductive coating liquid composition includes 10 to 70 wt% of PEDOT / PSS, 1 to 20 wt% of the organic binder, and 10 to 80% by weight of the organic solvent, 0.05-1% by weight of the silane coupling agent, and 0.02-0.4% by weight of the surfactant. The transparent conductive film for a flexible display according to item 13 or 14 of the scope of patent application, wherein the transparent base film comprises polyethylene terephthalate (PET) or colorless transparent polyimide (PI), The average thickness is 12 to 200 μm. The transparent conductive film for a flexible display according to item 13 or 14 of the scope of application for a patent, wherein the average thickness of the conductive layer is 100-1000 nm. The transparent conductive film for a flexible display according to item 13 or 14 of the scope of the patent application, wherein the transparent conductive film is bent 300,000 times under a state of applying a voltage of 5V so that the bending radius reaches 3 mm, and then used The change in surface resistance calculated by the following formula (1) is -5.0 to 5.0%: [Formula 1] . The transparent conductive film for a flexible display according to item 13 or 14 of the scope of application for a patent, wherein the surface resistance of the transparent conductive film is 100 ~ 200Ω / □, and it is cut into 10cm × 10cm × 50μm (length × width × thickness) The measured haze is less than 1%. The transparent conductive film for a flexible display according to item 13 or 14 of the scope of application for a patent, wherein the transparent conductive film has a transmittance of visible light of 80% or more, and a contact angle with water may be 60 to 85 °.